A polymeric system for the intra-oral delivery of an anti-fungal agent

Microbiological, physicomechanical, and surface evaluation of an experimental self-curing acrylic resin containing halloysite nanotubes doped with chlorhexidine

OBJECTIVE

The objective was to synthesize halloysite nanotubes loaded with chlorhexidine (HNT/CHX) and evaluate the antimicrobial activity, microhardness, color change, and surface characteristics of an experimental self-curing acrylic resin containing varying concentrations of the synthesized nanomaterial.

METHODS

The characterization of HNT/CHX was carried out by calculating incorporation efficiency, morphological and compositional, chemical and thermal evaluations. SAR disks were made containing 0 %, 3 %, 5 %, and 10 % of HNT/CHX. Specimens (n = 3) were immersed in distilled water and spectral measurements were carried out using UV/Vis spectroscopy to evaluate the release of CHX for up to 50 days. The antimicrobial activity of the composite against Candida albicans and Streptococcus mutans was evaluated by disk-diffusion test. Microhardness, color analyses (ΔE), and surface roughness (Ra) (n = 9) were performed before and after 30 days of immersion. Data were analyzed using ANOVA/Bonferroni. {Results.} The incorporation efficiency of CHX into HNT was of 8.15 %. All test groups showed controlled and cumulative CHX release up to 30 or 50 days. Significant antimicrobial activity was verified against both microorganisms (p < 0.001). After the 30-day immersion period, the 10 % HNT/CHX group showed a significant increase in hardness (p < 0.05) and a progressive color change (p < 0.001). At T0, the 5 % and 10 % groups exhibited Ra values similar to the control group (p > 0.05), while at T30, all groups showed similar roughness values (p > 0.05). {Significance.} The modification of a SAR with HNT/CHX provides antimicrobial effect and controlled release of CHX, however, the immediate surface roughness in the 3 % group was compromised when compared to the control group.

Novel bioactive dental restorations to inhibit secondary caries in enamel and dentin under oral biofilms

OBJECTIVE

To provide the first review on cutting-edge research on the development of new bioactive restorations to inhibit secondary caries in enamel and dentin under biofilms. State-of-the-art bioactive and therapeutic materials design, structure-property relationships, performance and efficacies in oral biofilm models.

DATA, SOURCES AND STUDY SELECTION

Researches on development and assessment new secondary caries inhibition restorations via in vitro and in vivo biofilm-based secondary caries models were included. The search of articles was carried out in Web of Science, PubMed, Medline and Scopus.

CONCLUSIONS

Based on the found articles, novel bioactive materials are divided into different categories according to their remineralization and antibacterial biofunctions. In vitro and in vivo biofilm-based secondary caries models are effective way of evaluating the materials efficacies. However, new intelligent and pH-responsive materials were still urgent need. And the materials evaluation should be performed via more clinical relevant biofilm-based secondary caries models.

CLINICAL SIGNIFICANCE

Secondary caries is a primary reason for dental restoration failures. Biofilms produce acids, causing demineralization and secondary caries. To inhibit dental caries and improve the health and quality of life for millions of people, it is necessary to summarize the present state of technologies and new advances in dental biomaterials for preventing secondary caries and protecting tooth structures against oral biofilm attacks. In addition, suggestions for future studies are provided.

Surface morphology and in vitro leachability of soft liners modified by the incorporation of antifungals for denture stomatitis treatment

OBJECTIVE

To evaluate the surface morphology and in vitro leachability of temporary soft linings modified by the incorporation of antifungals in minimum inhibitory concentrations (MIC) for Candida albicans biofilm.

METHODOLOGY

Specimens of soft lining materials Softone and Trusoft were made without (control) or with the addition of nystatin (Ny), miconazole (Mc), ketoconazole (Ke), chlorhexidine diacetate (Chx), or itraconazole (It) at their MIC for C. albicans biofilm. The surface analyses were performed using Confocal laser scanning microscopy after 24 h, 7 days, or 14 days of immersion in distilled water at 37ºC. In vitro leachability of Chx or Ny from the modified materials was also measured using Ultraviolet visible spectroscopy for up to 14 days of immersion in distilled water at 37ºC. Data (μg/mL) were submitted to ANOVA 1-factor/Bonferroni (α=0.05).

RESULTS

Softone had a more irregular surface than Trusoft. Morphological changes were noted in both materials with increasing immersion time, particularly, in those containing drugs. Groups containing Chx and It presented extremely porous and irregular surfaces. Both materials had biexponential release kinetics. Softone leached a higher concentration of the antifungals than Trusoft (p=0.004), and chlorhexidine was released at a higher concentration than nystatin (p<0.001).

CONCLUSIONS

The surface of the soft lining materials changed more significantly with the addition of Chx or It. Softone released a higher concentration of drugs than Trusoft did, guiding the future treatment of denture stomatitis.

Biological and Mechanical Properties of Denture Base Material as a Vehicle for Novel Hydroxyapatite Nanoparticles Loaded with Drug

Purpose: This study aimed to evaluate the biological and mechanical properties of the poly(methyl methacrylate) (PMMA) denture base material as a vehicle incorporating novel hydroxyapatite nanoparticles (HA-NP) loaded with metronidazole (MZ) drug.

Methods: HA-NP was prepared via wet-chemical-method, characterized by XRD, SEM/EDX, TEM, Fourier-transform infrared spectroscopy (FTIR), as well as the measurement of surface area and pore-size distribution. Four drug delivery formulas were prepared in the form of discs (10 x 2 mm) as follows: F1 (MZ/ HA-NP/PMMA), F2 (HA-NP/ PMMA), F3 (control-PMMA) and F4 (MZ/PMMA). Characterization of all formulas was performed using differential scanning calorimetry (DSC) and FTIR. MZ release rate, antimicrobial properties against three oral pathogens, cytotoxicity (MTT assay) and surface micro-hardness were also assessed. Statistical analysis of data was performed using one-way ANOVA test (P < 0.05).

Results: DSC thermograms showed compatibility among MZ, HA-NP and PMMA along with physical stability over 6 months storage period at room temperature. FTIR spectroscopy proved the absence of any possible chemical interaction with MZ. MZ-HA-NP/PMMA formula showed relatively better drug release compared to MZ-PMMA. Both formulas showed statistically significant antimicrobial potentials against two microbial strains. MTT demonstrated reduction in cell cytotoxicity after 96 hours with the least value for HA-NP. Surface micro-hardness revealed non-significant reduction compared with the control PMMA.

Conclusion: A novel biocompatible drug nanocarrier (HA-NP) was developed and incorporated in PMMA denture base material as a vehicle to allow prolonged sustained drug release to manage oral infections.

In vitro evaluation of physicochemical properties of soft lining resins after incorporation of chlorhexidine

STATEMENT OF PROBLEM

Incorporating chlorhexidine into soft lining materials has been suggested to reduce biofilm development on the material surface and treat denture stomatitis. However, evaluation of the physicochemical properties of this material is necessary.

PURPOSE

The purpose of this in vitro study was to evaluate the physicochemical properties of resin-based denture soft lining materials modified with chlorhexidine diacetate (CDA).

MATERIAL AND METHODS

Two soft lining resins were tested, one based on polymethyl methacrylate (PMMA) and the other on polyethyl methacrylate (PEMA), into which 0.5%, 1.0%, or 2.0% of CDA was incorporated; the control group had no CDA. The specimens were stored for 2 hours, 48 hours, 7, 14, 21, and 28 days and then analyzed for polymer crystallinity, Shore A hardness, degree of monomer conversion, residual monomer leaching, and CDA release. Data were analyzed by using a 3-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

The polymer crystallinity of PEMA and PMMA did not change after CDA incorporation. Shore A hardness increased over time, but not for any CDA concentrations tested after 28 days (P>.05). Considering the degree of conversion, PMMA-based resin showed no statistically significant difference (P>.05). However, PEMA-based resin showed a significant decrease (P<.05), which was reflected in a significant increase in residual monomer leaching from PEMA-based resin with the incorporation of 0.5% and 1.0% CDA (P<.05), mainly in the first 48 hours. PMMA-based resin showed no change in monomer leaching (P>.05). For both resins, the CDA release kinetics were related to monomer leaching; for PEMA-based resin, the values were significantly higher in the first 48 hours (P<.05), and for PMMA-based resin, the values were more sustained up to the last day of analysis.

CONCLUSIONS

The incorporation of CDA did not affect the physicochemical properties of soft resins. The properties of PMMA were better than those of PEMA.

Evaluation of the physical and antifungal effects of chlorhexidine diacetate incorporated into polymethyl methacrylate

This study aimed to evaluate the physical properties and antifungal activities of polymethyl methacrylate (PMMA) acrylic resins after the incorporation of chlorhexidine diacetate salt (CDA).

Nanocarriers with conjugated antimicrobials to eradicate pathogenic biofilms evaluated in murine in vivo and human ex vivo infection models

Conventional antimicrobials are becoming increasingly ineffective for treating bacterial infection due to the emergence of multi-drug resistant (MDR) pathogens. In addition, the biofilm-mode-of-growth of infecting bacteria impedes antimicrobial penetration in biofilms. Here, we report on poly(ethylene)glycol-poly(β-amino esters) (PEG-PAE) micelles with conjugated antimicrobials, that can uniquely penetrate biofilms, target themselves to bacterial cell surfaces once inside the low-pH environment of a biofilm and release conjugated antimicrobials through degradation of their ester-linkage with PAE by bacterial lipases. In vitro, PEG-PAE micelles with conjugated Triclosan (PEG-PAE-Triclosan) yielded no inadvertent leakage of their antimicrobial cargo and better killing of MDR Staphylococcus aureus, Escherichia coli and oral streptococcal biofilms than Triclosan in solution. In mice, PEG-PAE-Triclosan micelles with conjugated Triclosan yielded better eradication efficacy towards a MDR S. aureus-infection compared with Triclosan in solution and Triclosan-loaded micelles at equal Triclosan-equivalent concentrations. Ex vivo exposure of multi-species oral biofilms collected from orthodontic patients to PEG-PAE-Triclosan micelles, demonstrated effective bacterial killing at 30-40 fold lower Triclosan-equivalent concentrations than achieved by Triclosan in solution. Importantly, Streptococcus mutans, the main causative organism of dental caries, was preferentially killed by PEG-PAE-Triclosan micelles. Thus PEG-PAE-Triclosan micelles present a promising addendum to the decreasing armamentarium available to combat infection in diverse sites of the body. STATEMENT OF SIGNIFICANCE: pH-adaptive polymeric micelles with conjugated antimicrobials can efficiently eradicate infectious biofilms from diverse body sites in mice and men. An antimicrobial was conjugated through an ester-linkage to a poly(ethylene glycol) (PEG)/poly(β-amino ester) block copolymer to create micellar nanocarriers. Stable micelle structures were formed by the hydrophobic poly(β-amino ester) inner core and a hydrophilic PEG outer shell. Thus formed PEG-PAE-Triclosan micelles do not lose their antimicrobial cargo underway to an infection site through the blood circulation, but penetrate and accumulate in biofilms to release antimicrobials once inside a biofilm through degradation of its ester-linkage by bacterial lipases, to kill biofilm-embedded bacteria at lower antimicrobial concentrations than when applied in solution. PEG-PAE-Triclosan micelles effectively eradicate biofilms of multi-drug-resistant pathogens and oral bacteria, most notably highly cariogenic Streptococcus mutans, in mice and men respectively, and possess excellent clinical translation possibilities.

Peel bond strength and antifungal activity of two soft denture lining materials incorporated with 1% chlorhexidine diacetate

Two soft denture lining materials (SC-Soft Confort and TS-Trusoft) were investigated with and without the addition of 1.0% of chlorhexidine diacetate (1.0% CHX). To assess peel bond strength, specimens (75×10×6 mm) were submitted to a peel test at 10 mm/min immediately and after 24 h. To evaluate Candida albicans growth inhibition, disc of specimens (10×3 mm) were immersed in a solution with 3×10⁶ CFU/mL of C. albicans, and spectral measurements were made following immersion in MTT solution for 2, 4, and 6 days. The agar diffusion test was performed by investigating the diameters of inhibition zones around the disc of specimens (10×3 mm)after 48 h. Data were submitted to statistical analysis (α=0.05) and the failure modes were visually classified. The incorporation of 1.0% CHX significantly decreased the peel bond strength for TS (p=0.001) and SC (p=0.005) for immediate test and for TS after 24 h (p=0.010), but not for SC. C. albicans growth was decreased for both materials over time (p<0.05). SC presented inhibition zones approximately 2.0 times larger than TS. The incorporation of 1.0% CHX inhibited fungal growth without impairment to the peel bond strength for SC after 24 h.

Antibacterial dental adhesive resins containing nitrogen-doped titanium dioxide nanoparticles

The development of dental adhesive resins with long-lasting antibacterial properties is a possible solution to overcome the problem of secondary caries in modern adhesive dentistry.

OBJECTIVES

(i) Synthesis and characterization of nitrogen-doped titanium dioxide nanoparticles (N_TiO₂), (ii) topographical, compositional and wettability characterization of thin-films (unaltered and experimental) and, (iii) antibacterial efficacy of N_TiO₂-containing dental adhesives against Streptococcus mutans biofilms.

MATERIALS AND METHODS

Nanoparticles were synthesized and characterized using different techniques. Specimens (diameter = 12 mm, thickness ≅ 15 μm) of OptiBond Solo Plus (Kerr Corp., USA) and experimental adhesives [50, 67 and 80% (v/v)] were fabricated, photopolymerized (1000 mW/cm², 1 min) and UV-sterilized (254 nm, 800,000 μJ/cm²) for microscopy, spectroscopy, wettability and antibacterial testing. Wettability was assessed with a contact angle goniometer by dispensing water droplets (2 μL) onto four random locations of each specimen (16 drops/group). Drop profiles were recorded (1 min, 25 frames/s, 37 °C) and contact angles were calculated at time = 0 s (θ_INITIAL) and time = 59 s (θ_FINAL). Antibacterial testing was performed by growing S. mutans (UA159-ldh, JM10) biofilms for either 3 or 24 h (anaerobic conditions, 37 °C) with or without continuous light irradiation (410 ± 10 nm, 3 h = 38.75 J/cm², 24 h = 310.07 J/cm²) against the surfaces of sterile specimens.

RESULTS

N_TiO₂ was successfully prepared using solvothermal methods. Doped-nanoparticles displayed higher light absorption levels when compared to undoped titania. Experimental adhesives demonstrated superior antibacterial efficacy in dark conditions.

CONCLUSIONS

The findings presented herein suggest that N_TiO₂ is a feasible antibacterial agent against cariogenic biofilms.

In vivo study of antifungal effects of low-molecular-weight chitosan against Candida albicans

This study investigated the antifungal effects of low-molecular-weight chitosan solution on Candida albicans in denture stomatitis in comparison with nystatin suspension. This randomized, sing-leblind clinical trial included 40 patients diagnosed with denture stomatitis. Patients were divided into two groups, wherein one was treated with chitosan and the other with nystatin for 2 weeks. Changes in the erythematous area were recorded during and after treatment. A palatal smear was obtained for each patient before and after treatment to determine the number of blastospores and mycelia of C. albicans. The results were compared using the Mann-Whitney U test, revealing that the chitosan solution significantly decreased the erythematous surface area, burning sensation, time required for clinical improvement, and number of blastospores and mycelia. The antifungal efficacy of chitosan along with its inherent biocompatibility makes it a promising candidate for use as an antifungal mouthwash.

Peel bond strength of soft lining materials with antifungal to a denture base acrylic resin

The effect of the addition of nystatin, miconazole, ketoconazole, chlorhexidine, and itraconazole into the soft lining materials Softone and Trusoft on their peel bond strength to a denture base acrylic resin was evaluated. Specimens of soft lining materials (n=7) were made without (control) or with the incorporation of antifungals at their minimum inhibitory concentrations to the biofilm of C. albicans and bonded to the acrylic resin. Peel testing was performed after immersion in distilled water at 37ºC for 24 h, 7 and 14 days. Data (MPa) were analyzed by 3-way ANOVA/Tukey-Kramer test (α=0.05) and the failure modes were classified. The addition of nystatin and ketoconazole did not affect the peel bond strength for up to 14 days. Most failures were predominantly cohesive within soft lining materials. With the exception of itraconazole, incorporating the antifungals into the soft lining materials did not result in values below those recommended for peel bond strength after 7 and 14 days of analysis.

Resins-based denture soft lining materials modified by chlorhexidine salt incorporation: an in vitro analysis of antifungal activity, drug release and hardness

OBJECTIVES

To evaluate the in vitro growth inhibition of Candida albicans, the rate of chlorhexidine release and shore A hardness from resins-based denture soft lining materials modified by chlorhexidine diacetate (CDA) or chlorhexidine hydrochloride (CHC) incorporation.

METHODS

Resin discs were prepared from soft denture liners based on poly (methyl methacrylate) (PMMA) or poly (ethyl methacrylate) (PEMA) containing 0.5, 1.0 and 2.0 wt.% of CDA or CHC. For antifungal activity resin discs were placed on agar plates inoculated with C. albicans, after 48 h at 37°C the diameters of inhibition zones were measured. For the chlorhexidine release, discs were immersed into distilled water at 37°C, and spectral measurements were made after 48 h. Shore A hardness was evaluated at the baseline, 2 and 7 days, using 6mm thick rectangular specimens also immersed into distilled water at 37°C. Data were statistically processed by SigmaStat software using ANOVA and all pairwise multiple comparison procedures was done using the Holm-Sidak method, with α=0.05 (p<0.001).

RESULTS

CDA added to PMMA soft liner and PEMA soft liner had a dose-related inhibitory effect on C. albicans and on chlorhexidine release rate (p<0.001). The PMMA and PEMA hardness increased statistically by time but not for the different CDA concentrations. CHC had no inhibitory effect on C. albicans.

SIGNIFICANCE

Chlorhexidine diacetate released from resins-based soft lining materials can be convenient to reduce the biofilm development on the material surface and treat denture stomatitis, without depending on patient compliance.

Fracture toughness of heat cured denture base acrylic resin modified with Chlorhexidine and Fluconazole as bioactive compounds

PURPOSE

This study investigated the impact of incorporating Chlorhexidine and Fluconazole as bioactive compounds on the fracture toughness of conventional heat cured denture base acrylic resin material (PMMA).

MATERIALS AND METHODS

30 single edge-notched (SEN) samples were prepared and divided into three groups. 10% (mass) Chlorhexidine and 10% (mass) Diflucan powder (4.5% mass Fluconazole) were added to heat cured PMMA respectively to create the two study groups. A third group of conventional heat cured PMMA was prepared as the control group. Fracture toughness (3-point bending test) was carried out for each sample and critical force (Fc) and critical stress intensity factor (KIC) values measured. Data were subject to parametric statistical analysis using one-way ANOVA and Post hoc Bonferroni test (p=0.05).

RESULTS

Fluconazole had no significant effect on the fracture toughness of the PMMA while Chlorhexidine significantly reduced the KIC and therefore affected the fracture toughness.

CONCLUSION

When considering addition of a bioactive material to PMMA acrylic, Chlorhexidine will result in reduced fracture toughness of the acrylic base while Fluconazole has no effect.

Mass uptake study of the diffusion of water and SBF into poly(2-hydroxyethyl methacrylate-co-tetrahydrofurfuryl methacrylate) containing aspirin or vitamin B12

The ingress of water and Kokubo simulated body fluid (SBF) into poly(2-hydroxyethyl methacrylate) (PHEMA), and its co-polymers with tetrahydrofurduryl methacrylate (THFMA), loaded with either one of two model drugs, vitamin B12 or aspirin, was studied by mass uptake over the temperature range 298-318 K. The polymers were studied as cylinders and were loaded with either 5 wt% or 10 wt% of the drugs. From DSC studies it was observed that vitamin B12 behaved as a physical cross-linker restricting chain segmental mobility, and so had a small anti-plasticisation effect on PHEMA and the co-polymers rich in HEMA, but almost no effect on the Tg of co-polymers rich in THFMA. On the other hand, aspirin exhibited a plasticising effect on PHEMA and the co-polymers. All of the polymers were found to absorb water and SBF according to a Fickian diffusion mechanism. The polymers were all found to swell to a greater extent in SBF than in water, which was attributed to the presence of Tris buffer in the SBF. The sorptions of the two penetrants were found to follow Fickian kinetics in all cases and the diffusion coefficients at 310 K for SBF were found to be smaller than those for water, except for the polymers containing aspirin where the diffusion coefficients were higher than for the other systems. For example, for sorption into PHEMA the diffusion coefficient for water was 1.41 x 10(-11) m2/s and for SBF was 0.79 x 10(-11) m2/s, but in the presence of 5 wt% aspirin the corresponding values were 1.27 x 10(-11) m2/s and 1.25 x 10(-11) m2/s, respectively. The corresponding values for PHEMA loaded with 5 wt% B12 were 1.25 x 10(-11) m2/s and 0.74 x 10(-11) m2/s, respectively.

Antibacterial and physical properties of calcium-phosphate and calcium-fluoride nanocomposites with chlorhexidine

OBJECTIVES

Previous studies have developed calcium phosphate and fluoride releasing composites. Other studies have incorporated chlorhexidine (CHX) particles into dental composites. However, CHX has not been incorporated in calcium phosphate and fluoride composites. The objectives of this study were to develop nanocomposites containing amorphous calcium phosphate (ACP) or calcium fluoride (CaF(2)) nanoparticles and CHX particles, and investigate Streptococcus mutans biofilm formation and lactic acid production for the first time.

METHODS

Chlorhexidine was frozen via liquid nitrogen and ground to obtain a particle size of 0.62 μm. Four nanocomposites were fabricated with fillers of: nano ACP; nano ACP+10% CHX; nano CaF(2); nano CaF(2)+10% CHX. Three commercial materials were tested as controls: a resin-modified glass ionomer, and two composites. S. mutans live/dead assay, colony-forming unit (CFU) counts, biofilm metabolic activity, and lactic acid were measured.

RESULTS

Adding CHX fillers to ACP and CaF(2) nanocomposites greatly increased their antimicrobial capability. ACP and CaF(2) nanocomposites with CHX that were inoculated with S. mutans had a growth medium pH>6.5 after 3 d, while the control commercial composites had a cariogenic pH of 4.2. Nanocomposites with CHX reduced the biofilm metabolic activity by 10-20 folds and reduced the acid production, compared to the controls. CFU on nanocomposites with CHX were three orders of magnitude less than that on commercial composite. Mechanical properties of nanocomposites with CHX matched a commercial composite without fluoride.

SIGNIFICANCE

The novel calcium phosphate and fluoride nanocomposites could be rendered antibacterial with CHX to greatly reduce biofilm formation, acid production, CFU and metabolic activity. The antimicrobial and remineralizing nanocomposites with good mechanical properties may be promising for a wide range of tooth restorations with anti-caries capabilities.

Study of the elution of fluconazole from a self-polymerizing acrylic resin and its activity against resistant Candida albicans

The study aimed, firstly, to monitor the release of an antifungal drug, fluconazole, from a self-polymerizing poly(methyl methacrylate) (PMMA) denture base resin in artificial saliva and comparing it with the release in water; and secondly, to investigate the effect of the released drug on the growth of resistant and standard strains of Candida albicans. A high-performance liquid chromatography-ultra-violet (HPLC-UV) method was used in the analysis of the released eluates into distilled water from self-polymerized PMMA discs doped with the 10% fluconazole antifungal drug. The efficacy of the released drug against resistant and standard strains of C. albicans was monitored, using agar diffusion method. The results showed that fluconazole, can be successfully incorporated with the self-polymerized PMMA. The findings suggest that the drug leaches steadily out of the PMMA resin into artificial saliva and distilled water at mouth temperature and that sustained drug release continued throughout the 28 days test period. It was shown that the released drug demonstrated antifungal activity against both standard and resistant C. albicans. The findings of this investigation have a clinical value in terms of their significant contribution to the treatment of fungal infections of the oral cavity. The sustained release of antifungal drug from the PMMA resin clearly constitutes a new dosage form of the drug via the poly(methyl methacrylate) delivery system.

New form of administering chlorhexidine for treatment of denture-induced stomatitis

Background:

The purpose of this study was to evaluate the release of chlorhexidine as an antifungal drug from doped self-cured poly (methyl methacrylate) (PMMA) acrylic resin and the effect of the drug released on the growth of Candida albicans.

Methods:

Release of chlorhexidine was evaluated using liquid chromatography, and the effect of the drug on the growth of C. albicans was investigated microbiologically using a “well” technique on Saboraud culture medium inoculated with a resistant strain of C. albicans.

Results:

Chlorhexidine leached steadily out of the acrylic resin into distilled water at mouth temperature, and the sustained drug release continued throughout the 28-day test period. The drug released also demonstrated antifungal activity against the resistant strain of C. albicans.

Conclusion:

The findings of this study support the use of chlorhexidine-impregnated self-cured PMMA chair-side resin as a new dosage form for the treatment of denture-induced stomatitis.

In vitro drug release study of methacrylate polymer blend system: effect of polymer blend composition, drug loading and solubilizing surfactants on drug release

The application of polymers as the drug delivery systems for treating oral infections is a relatively new area of research. The present study was to test the release of the antibacterial drug chlorhexidine diacetate (CHDA), the antifungal drug Nystatin (NYS) and the antiviral drug acyclovir (ACY) from polymer blends of poly(ethyl methacrylate) and poly(n-hexyl methacrylate) of different compositions. The effects of polymer blend composition, drug loading and solubilizing surfactants on the release of the drugs have been studied. Measurements of the in vitro rate of drug release showed a sustained release of drug over extended periods of time. Drug release rates decreased with increasing PEMA content in polymer blends. CHDA release rates increased steadily with increasing drug load. The drug release rates increased with the addition of surfactants. This study demonstrates that the three therapeutic agents show a sustained rate of drug release from polymer blends of PEMA and PHMA over extended periods of time. By varying polymer blend compositions as well as the drug concentration (loading), it is possible to control the drug release rates to a desired value. The drug release rate is enhanced by addition of surfactants that solubilize drugs in the polymer blends.

Development of remineralizing, antibacterial dental materials

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90microm) and beta-tricalcium phosphate (beta-TCP) at 1:1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24h, the remaining MCPM had reacted with water and beta-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.

EVA copolymer matrix for intra-oral delivery of antimicrobial and antiviral agents

Biocompatible ethylene vinyl acetate copolymer (EVA) was utilized to study the release of an antiviral drug (acyclovir (ACY)) and an antimicrobial drug (doxycycline hyclate (DOH)). Release of both drugs from EVA was measured individually and in combination. The effect of drug combination of DOH and ACY is presented. Additionally, the release rate of DOH after coating of the matrix with a different copolymer, in drug-loading with increasing loads of DOH, and with increases in temperature are also presented. The drugs incorporated in EVA films were prepared from the dry sheet obtained by solvent evaporation of polymer casting solutions with drugs. Drug release from the films was examined for about 12 days in distilled water at 37 degrees C. Changes in optical density were followed spectrophotometrically. The combination of ACY and DOH resulted in an increased release of ACY by about three times (P < 0.001) while DOH showed a decrease in rate of about two times compared to the individual release rates (P = 0.008). Increases in drug levels of DOH resulted in increases in drug release rates (P = 0.001). The release rate of DOH increased with temperature (P = .001; 27, 32, 37 and 42 degrees C were studied) and the energy of activation (DeltaE ( not equal) = 56.69 kJ/mol) was calculated using the Arrhenius equation for the diffusion of DOH molecules. Thus, the release rates of drugs were influenced by many factors: drug combination, coating the device, drug-loading, and temperature variation. Therefore it is proposed that controlling these variables should make it possible to obtain therapeutic levels of drugs released from drug loaded polymer, which may be beneficial in treating oral infections.

Controlled Release of Chlorhexidine Diacetate from a Porous Methacrylate System: Supercritical Fluid Assisted Foaming and Impregnation

The release of chlorhexidine diacetate (CX) from a self-curing polymeric system based on poly(ethylmethacrylate) and tetrahydrofurfurylmethacrylate (PEM/THFM) was developed in this study. Supercritical fluid assisted impregnation and foaming was employed for preparing porous CX-PEM/THFM drug release system. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) show that the crystallinity of CX significantly decreased after supercritical processing, whilst Raman spectroscopy suggested a hydrogen bonding interaction between the CX and PEM in the product. A UV-Vis dissolution study revealed that the drug release rate is almost as seven times faster in the SCF processed drug delivery system than conventional cured samples.

Controlled release of chlorhexidine from UDMA-TEGDMA resin

Chlorhexidine salts are available in various formulations for dental applications. This study tested the hypothesis that the release of chlorhexidine from a urethane dimethacrylate and triethylene glycol dimethacrylate resin system can be effectively controlled by the chlorhexidine diacetate content and pH. The filler concentrations were 9.1, 23.1, or 33.3 wt%, and the filled resins were exposed to pH 4 and pH 6 acetate buffers. The results showed that Fickian diffusion was the dominant release mechanism. The rates of release were significantly higher in pH 4 buffer, which was attributed to the increase of chlorhexidine diacetate solubility at lower pH. The higher level of filler loading reduced the degree of polymerization, leading to a greater loss of organic components and higher chlorhexidine release rates.

Characterisation of some experimental silicones

Release of antimicrobials/antibacterials like chlorhexidine diacetate (CHD) has proved successful in inhibiting Candidal colonisation of silicone-based biomaterials. However, their addition will increase water uptake and may compromise the mechanical integrity. Two experimental silicones (S1 and S2) differing only in the surface treatment of the filler, were investigated. Ultimate tensile strength (UTS), % elongation at break (Eb), Shore A hardness and, when doped with 1% CHD, water uptake and CHD release were measured. Elastic modulus (E) was calculated from the hardness measurements. There was no significant difference in UTS and Eb between the two materials. However S1 had a higher hardness (30.6 +/- 0.97) and thus E (0.76 MPa) than S2 (hardness = 23.8 +/- 0.48, E = 0.45 MPa). Water uptake for S2 (0.6%) was higher than for S2 (0.1) and addition of CHD dramatically increased the uptake of both (S1 = 3.1%, S2 = 4.0%). Release of CHD was higher for S2 (30%) than S1 (27%). Equating osmotic pressure within the droplets with elastic restraining force gave an extension ratio of 1.95 for S1 and 5.39 for S2. Thus, addition of a hydrophilic agent can compromise the mechanical integrity of low modulus silicones.

Effect of the Association of Nystatin with a Tissue Conditioner on its Ultimate Tensile Strength

PURPOSE

This study evaluated the ultimate tensile strength of a tissue conditioner without nystatin incorporation (GI-control group) and the same tissue conditioner modified by the addition of nystatin in two concentrations: GII-500,000 International Units (U) and GIII-1,000,000 U, in which each milligram of the medicament corresponded to 6079 U.

MATERIALS AND METHODS

Dumbbell-shaped specimens (N= 7) with a central cross-sectional area of 33 x 6 x 3 mm were produced for the three experimental groups. After polymerization following manufacturer's instructions, specimens were immersed in distilled water at 37 degrees C for either 24 hours or 7 days and then tested in tension in the MTS 810 at 40 mm/minute. Data were analyzed by two-way ANOVA followed by Tukey's test, at 95% level of confidence.

RESULTS

The means (force-grams (gf) +/- standard deviation) of the ultimate tensile strength were: GI-634.29 +/- 122.80; GII-561.92 +/- 133.56; and GIII-547.30 +/- 73.47 for 24-hour storage, and GI-536.68 +/- 54.71; GII-467.50 +/- 143.51; and GIII-500.62 +/- 159.76 for 7-day storage. There were no statistically significant differences among the three experimental groups (p > 0.05). The ultimate tensile strength means of all experimental groups after 7 days were significantly lower than those observed after 24 hours (p= 0.04).

CONCLUSIONS

The results of this study suggest that the addition of nystatin into the tissue conditioner investigated in concentrations below 1,000,000 U did not affect its ultimate tensile strength.

Supercritical carbon dioxide: putting the fizz into biomaterials

This paper describes recent progress made in the use of high pressure or supercritical fluids to process polymers into three-dimensional tissue engineering scaffolds. Three current examples are highlighted: foaming of acrylates for use in cartilage tissue engineering; plasticization and encapsulation of bioactive species into biodegradable polyesters for bone tissue engineering; and a novel laser sintering process used to fabricate three-dimensional biodegradable polyester structures from particles prepared via a supercritical route.

Chlorhexidine-releasing methacrylate dental composite materials

Light curable antibacterial, dental composite restoration materials, consisting of 80 wt% of a strontium fluoroaluminosilicate glass dispersed in methacrylate monomers have been produced. The monomers contained 40-100 wt% of a 10 wt% chlorhexidine diacetate (CHXA) in hydroxyethylmethacrylate (HEMA) solution and 60-0 wt% of a 50/50 mix of urethane dimethacrylate (UDMA) and triethyleneglycol dimethacrylate (TEGDMA). On raising HEMA content, light cure polymerisation rates decreased. Conversely, water sorption induced swelling and rates of diffusion controlled CHXA release from the set materials increased. Experimental composites with 50 and 90 wt% of the CHXA in HEMA solution in the monomer were shown, within a constant depth film fermentor (CDFF), to have slower rates of biofilm growth on their surfaces between 1 and 7 days than the commercial dental composite Z250 or fluoride-releasing dental cements, Fuji II LC and Fuji IX. When an excavated bovine dentine cylinder re-filled with Z250 was placed for 10 weeks in the CDFF, both bacteria and polymers from the artificial saliva penetrated between the material and dentine. With the 50 wt% experimental HEMA/CHXA formulation, this bacterial microleakage was substantially reduced. Polymer leakage, however, still occurred. Both polymer and bacterial microleakage were prevented with a 90 wt% HEMA/CHXA restoration in the bovine dentine due to swelling compensation for polymerisation shrinkage in combination with antibacterial release.

Vitamin B12 Release from P(HEMA-co-THFMA) in Water and SBF: A Model Drug Release Study

A model drug release study on the ingress of water and Kokubo simulated body fluid (SBF) into poly(2-hydroxyethyl methacrylate) (P(HEMA)) and its copolymers with tetrahydrofurfuryl methacrylate (THFMA) loaded with vitamin B12 was undertaken over the temperature range 298–318 K. The polymers were studied as cylinders and were loaded with either 5 or 10 wt-% of the drug. The drug release from the polymers was found to follow a Fickian diffusion mechanism in the early stages of the drug release, with higher normalized release rates at higher temperatures and higher drug loadings. The normalized release rates were also found to be higher for the SBF solution than for water. The copolymer composition was found to have a significant effect on the rate of release of the drug, with the rate falling rapidly between HEMA mole fractions of 1.0 and 0.8, but for lower mole fractions of HEMA the normalized release rate decreased more slowly. This behaviour followed the trend found for the changes in the equilibrium penetrant contents for the copolymers.